Electrooptical method and apparatus



1935. R. E. WALLACE ELECTROOPTICAL METHOD AND APPARATUS Filed Sept. 6, 1950 11 E ii Riel-mm 564K "44mm:

. INVENTOR 7 BY AQ KZvM ATTORNEY S Patented Feb. 12, 1935 UNITED STATES PATENT OFFICE ELECTROOPTICAL METHOD AND Y APPARATUS Richard Edgar Wallace, New York, N. Y., assignor, by mesne assignments, to Radio Corporation of America, a corporationof Delaware This invention relates to electro-optical systems, and with particularity to methods and means for scanning in television transmission facsimile and similar systems.

5 I An object of the invention is to provide a more efiicient method of scanning objects, images or visual representations.

Various methods of scanning have heretofore been devised. However, there are two typical systems, one employing a perforated rotatable member such as a disc, drum, band, or the like, and the other employing the same type of member as a carrier for lenses. In the case of the perforated scanner an exceedingly large proportion of the scanning beam is waster, sinceonly a minute portion of the beam passes through the scanning perforations to the object to be scanned. In the case of the lens type scanner this difficulty is in a great measure overcome. However,the 20 lens type of scanner is very expensive to construct, and there is a certain percentage of the light lost in passing through the lenses.

Accordingly it is another object of the invention to provide a novel type of scanner possessing 25 all the advantages of the usual lens disc or lens drum scanner, and which is simple of construction and economical of manufacture.

While the scanner to be described hereinafter is applicable in general to any system requiring an' object to be scannedor illuminated in successive elemental areas, the invention finds its greatest practical import in connection with the scanning or illumination of motion picture films. In the usual-type of motion picture film scanning the practice has been toilluminate theentire scanning field of the scanner by a very large beam of light. As the scanner rotates it selects successive small portions of. this beam and projects them through the continuously moving film. Obvious- 40 ly, an exceedingly bright light must be employed in order that a beam of requisite intensity may pass through the individual scanning apertures.

In accordance with the present invention, this and other disadvantages are overcome by limiting thescanning beam proper to "a very small cross section, preferably'of the same order as the area of the scanning apertures.

Accordingly a feature of-the invention relates to a method of moving a concentrated scanning {50 beam of small cross section in a point by point fashion across an object or visual representation to be scanned.

Another feature of the invention relates to a combination scanner in the form of a perforated disc and a. rotatable carrier having a plurality: of

disc 6.

light-reflecting and/or concentrating devices corresponding to the scanning perforations.

Another'feature of the invention relates to a method of scanning a motion picture film by projecting substantially all the light from a scan- 1 ning light source in successive scanning spots upon the film. g 7

While the invention will be described hereinafter as applied to a scanner used for transmitting, it will be understood that the invention is equally applicable for receiving or synthesizing electro-optical images or representations.

Referring to the drawing- Fig. 1 represents in schematic form sufficient portions of a television system to enable the invention'to be clearly understood; and

Fig. 2 is another View of the apparatus of Fig. 1, showing more clearly the disposition and arrangement of the individual elements thereof.

Referring more particularly to the drawing, the numeral 1 represents a source of scanning light such as an arc lamp or other light source of high and constant intensity. Positionedin optical alignment with the source 1 is a suitable lens system 2 for collecting substantially all the light from said source and reducing it to a concentrated beam of relatively small cross section. The numeral 3 represents the object or. representation to be scanned, which for the sake of illustration will be chosen as a continuously moving motion'pic'ture film adapted to be fed by any suitable mechanism (not shown) in the directionof the arrows (Fig. l). Positioned adjacent'to the moving film 3 is an aperture plate 4 having a slit 5 therein of slightly'less width than the film 3. Positioned in front of the plate 4 and adapted to rotate in a plane parallel to said plate is a disc 6 mounted on shaft 7. Shaft 7 is connected to any suitable source of motive power (not shown) for rotating the disc at the proper rate of speed. Attached to disc 6 at equal intervals therearound are a series of small mirrors or other light reflecting members 8. As shown more clearly in Fig. 2, these mirrors are preferably mounted on disc 6, soas to sustain an angle of substantially 45 with the plane of the disc. With this particular angle of mounting the light source 1 may be disposed so that the beam 9 therefrom is directed almost parallel to the disc 6. Con sequently when the beam 9 is reflected from the individual mirrors 8 in succession it is reflected in a path substantially perpendicular to the In any event the mirrors may be designed so as to control the direction of the reflected beam while it is moving, as described hereinafter. I

It will be obvious of course that this particular arrangement of the light beam and mirrors is not absolutely necessary. Thus the mirrors may be mounted at any other angle on the disc 6 and the stationary beam 9 may be directed at a suitable angle upon the mirrors. The number 'of mirrors on the disc 6 will of course depend upon the scanning detail required. In accordance with the standardpractice the disc 6 may be provided with a' set of 48 mirrors equally spaced around the disc. It will be obvious of course that the disc 6 and/or the distance of the mirrors from the center of the disc will preferably be so chosen that the interval between successive mirrors is slightly greater than the width of the film 3, .or the slit 5, so that only one mirror at a time traverses the slit when the disc is rotating.

'From the, foregoing arrangement it will be obvious, therefore that as the disc 6 rotates in the direction of the arrow, the stationary-light beam 9'impinges in succession upon each of the mirrors 8. -Consequently if the stationary beam is directed in "substantial alignment with the slit- 5 it illuminates only one of the mirrors 8 at a time since each successive mirror comes into alignment with the beam 9, just as the preceding mirror is coming out of alignment with the said beam. It will be understood, of course that the disc 6 ispreferably, although not necessarily large enough sothat the path traced by each of the mirrors is substantially linear. r y

Mounted adjacent to the disc 6'and adapted to rotate in a plane parallel thereto is another disc 10 having a plurality of scanning apertures 11 therein, there being one of these scanning apertures'for each of the mirrors 8. The disc 10 may be fastened to the shaft 7 or it may 'be mounted on an independent shaft and rotated in synchronism withdisc 6. by well'kn'own means. It is preferred, however, to mount the discs 6 and'lO on the same shaft, so that each of the scanning perforations 11 is in alignment with a corresponding mirror 8 on the disc 6. Any suitable optical system schematically represented by the numeral 12 may be interposed betweenthe discs so as'to project the light spot reflected from the mirrors 8, through the corresponding perforations 11. Situated on the opposite sides of the disc 10 is a light translating device 13 such as a photo-electric cell or the like, and if desired, a lens system 14 may be interposed between the .disc 10 and the device 13 to collect the light pass ing through the perforations 11 projected upon the cell 13. 1

From the foregoing it will be obvious therefore that since the film- 3 moves continuously in the direction'of thearrowand the disc 6 rotates in the direction shown, theifilm 3 is illuminated by a moving spot of light which moves transversely across the slit 5 as represented by the dotted arrows (Fig. '2). The mirrors 8, therefore, as

they move across the slit 5, trace successive linear strips across the width of the film and the disc 10, rotating in special synchronism with the disc 6, selects the elemental areas of the spot illuminated portions of the film 3, which selected portions are then projected upon the cell 13.

If desired the mirrors 8 may be concave so as ;to focus the light spot from stationary beam 9 in the form of a small minute spot upon the film 3. In this case the disc 10 may be dispensed with and cell 13 may be illuminated directly by thelight spot passing through the film.

hated.-

The foregoing description is predicated upon a continuously moving picture film. However, where the film is fed intermittently the mirrors 8 will then be arranged in a spiral path around the disc 6 and the light from source 1 instead of being projected in the form of a spot will be projected in the form of an intense narrow strip corresponding. to the radial displacement of the first and last mirrors of the spiral series. It will be obvious of course in this latter arrangement that the plate 4 instead of being providedwith a slit .may be provided with a rectangular or square opening corresponding to the dimensions of the picture film; This latter arrangement of course willbe equally applicable for the reproduction of televisionimages since the source 1 may be replacecl by a neon lamp or other well known device for producing modulated light beams under cont'rollof image currents;

While specific apparatus and arrangements have been described, it is understood that the invention is not limited thereto, and that various modifications and changes may be made therein.

tionary light to illuminate the film in successive concentrated light spots, directly imaging the film as it is illuminated on the other scannerindependently of the firstscanner, and rotating said other scanner to select elemental areas of each spot as it is imaged thereupon.

2. The method'of scanning a transparent film for television transmission employing two sepa-' rate rotatable 'scanne'rs on opposite sides'of the film each having the same number of scanning elements, which comprises using one scanner to illuminate said entire film in a series of successive concentrated light spots, directly "imaging said entire area as illuminated upon the other scanner and independently of the first scanner,

and rotating saidother scanner in synchronism with the other scanner to select elemental portions of eachspot of said area as itis illumi- 7 3. Ina system for scanning a transparent film for imaging transmission, a first scanner, a second scanner, said scanners being on opposite sides of'said film, each of said scanners havi the same number of scanning elements, a stationary light beam, means for rotating the first scanner'across said beam to, light the film in successive concentrated light spots, meansfor imaging the illuminated spots of the film'direct-' 1y upon the second scanner, and means for rotating the second scanner in synchronism with the first scanner to select elemental portions of each spot of the object as it is illuminated.

4. In a system for scanning a transparent film' for image transmission, a first scanner, a'second scanner, said scanners being on opposite sides of said film, each of said scanners having the same number of scanning elements, a stationary light beam, means for rotating the first scanner across said beam to illuminate the object whose image is to be transmitted in successive concentrated reflected light spots, means for directly imaging the entire area on the second scanner independently of the first scanner, and means for rotating the second scanner in synchronism with the first scanner to select elemental areas of each concentrated spot imaged thereupon.

5. In a scanning system for television transmission, the combination of a rotatable carrier having mounted thereon a plurality of separate light reflecting elements, a stationary concentrated light beam, a transparent film, means for rotating said carrier to bring each of said elements successively in the path of said beam to produce corresponding moving light spots for scanning said film, and a separate apertured scanning device rotating in synchronism with said carrier but on the opposite side of said film therefrom for selecting the elemental areas of the moving light spots, all the apertures in said scanning device being in alignment with said reflecting elements on said carrier.

6. A scanning system according to claim in which the said scanning device is provided with a plurality of scanning apertures, one for each of the light reflecting elements.

7. A scanning system according to claim 5 in which each of said light reflecting members is in the form of a plain mirror mounted at an angle to the plane of the carrier.

8. A scanning system according to claim 5 in which the carrier is in the form of a disc and the light reflecting members are in the form of concave mirrors. V

9. In a scanning system the combination of a rotatable scanner having a plurality of separate light reflecting scanning elements mounted thereon, the number of scanning elements being equal to the number of linear elements to be scanned, another apertured scanner having an aperture for each of said light reflecting ele-- ments, a transparent film between said scanners, and means for rotating said scanners in synchronism, whereby all the apertures in said other scanner are at all times in optical alignment with all the corresponding light reflecting elements.

10. In a scanning system the combination of a disc carrying a plurality of separate scanning mirrors, one for each of the linear elements to be scanned; means for projecting a stationary light spot upon said mirrors, a transparent film to be scanned, means for rotating said disc to reflect said light spot through said film in the form of a moving spot, and another disc having apertures in alignment with the mirrors for selecting elemental areas of said light spot as it is moving.

11. A scanning system comprising a disc carrying a plurality of separate mirrors, one for each linear element of the image to be scanned, means for projecting a stationary light spot upon said mirrors, a transparent film, means for rotating said mirrors to reflect said light spot through said film in the form of a moving light spot, a second disc on the other side of said film rotating in synchronism with the first disc, and having a plurality of scanning apertures, one for eachof said mirrors, for selecting elemental areas of each spot reflected from the mirrors and in alignment thereon, and an object to be scanned positioned so as to receive the moving light spot reflected from said mirrors passing through the apertures in the second mentioned disc.

12. Means for scanning motion picture films comprising a rotating carrier carrying a plurality of separate light reflecting elements one for each linear element of the image to be scanned, a rotating scanner having a plurality of apertures of elemental area, one for each of said light reflecting elements for selecting elemental areas of each light beam reflected from said light reflecting elements, means for rotating said carrier and said scanner in synchronism, a motion picture film adjacent said scanner, and an apertured plate between said rotating scanner and said motion picture film.

13. The method of scanning a motion picture film which comprises moving said film continuously in one direction, moving a scanning spot transversely across said film, limiting the size of said spot upon said film, and separately scanning said film as illuminated by said spot to select from each illuminated spot an elemental area thereof.

RICHARD EDGAR WALLACE. 

